3G84

Crystal structure of the trimeric neck and carbohydrate recognition domain of R343V mutant of human surfactant protein D in complex with alpha 1,2 dimannose.

Summary for 3G84

• Entry DOI: 10.2210/pdb3g84/pdb
• Related: 2ggu 2ggx 2orj 2ork 2os9 2ria 3G81 3G83
• Related PRD ID: PRD_900111
• Descriptor: Pulmonary surfactant-associated protein D, alpha-D-mannopyranose-(1-2)-alpha-D-mannopyranose, CALCIUM ION, ... (4 entities in total)
• Functional Keywords: surfactant protein, carbohydrate recognition domain, trimeric, collagen, extracellular matrix, gaseous exchange, glycoprotein, hydroxylation, lectin, secreted, surface film, sugar binding protein
• Biological source: Homo sapiens (man)
• Total number of polymer chains: 3
• Total formula weight: 53030.03

Authors

Head, J.F. (deposition date: 2009-02-11, release date: 2009-03-17, Last modification date: 2024-11-06)

Primary citation

Crouch, E.,Hartshorn, K.,Horlacher, T.,McDonald, B.,Smith, K.,Cafarella, T.,Seaton, B.,Seeberger, P.H.,Head, J.
Recognition of mannosylated ligands and influenza A virus by human surfactant protein D: contributions of an extended site and residue 343.
Biochemistry, 48:3335-3345, 2009

PubMed Abstract: Surfactant protein D (SP-D) plays important roles in antiviral host defense. Although SP-D shows a preference for glucose/maltose, the protein also recognizes d-mannose and a variety of mannose-rich microbial ligands. This latter preference prompted an examination of the mechanisms of mannose recognition, particularly as they relate to high-mannose viral glycans. Trimeric neck plus carbohydrate recognition domains from human SP-D (hNCRD) preferred alpha1-2-linked dimannose (DM) over the branched trimannose (TM) core, alpha1-3 or alpha1-6 DM, or D-mannose. Previous studies have shown residues flanking the carbohydrate binding site can fine-tune ligand recognition. A mutant with valine at 343 (R343V) showed enhanced binding to mannan relative to wild type and R343A. No alteration in affinity was observed for D-mannose or for alpha1-3- or alpha1-6-linked DM; however, substantially increased affinity was observed for alpha1-2 DM. Both proteins showed efficient recognition of linear and branched subdomains of high-mannose glycans on carbohydrate microarrays, and R343V showed increased binding to a subset of the oligosaccharides. Crystallographic analysis of an R343V complex with 1,2-DM showed a novel mode of binding. The disaccharide is bound to calcium by the reducing sugar ring, and a stabilizing H-bond is formed between the 2-OH of the nonreducing sugar ring and Arg349. Although hNCRDs show negligible binding to influenza A virus (IAV), R343V showed markedly enhanced viral neutralizing activity. Hydrophobic substitutions for Arg343 selectively blocked binding of a monoclonal antibody (Hyb 246-05) that inhibits IAV binding activity. Our findings demonstrate an extended ligand binding site for mannosylated ligands and the significant contribution of the 343 side chain to specific recognition of multivalent microbial ligands, including high-mannose viral glycans.

PubMed: 19249874
DOI: 10.1021/bi8022703

Experimental method

X-RAY DIFFRACTION (2.3 Å)